classicvalues / lockfile-1

A very polite lock file utility, which endeavors to not litter, and to wait patiently for others.

lockfile

A very polite lock file utility, which endeavors to not litter, and to wait patiently for others.

Usage

var lockFile = require('lockfile')

// opts is optional, and defaults to {}
lockFile.lock('some-file.lock', opts, function (er) {
  // if the er happens, then it failed to acquire a lock.
  // if there was not an error, then the file was created,
  // and won't be deleted until we unlock it.

  // do my stuff, free of interruptions
  // then, some time later, do:
  lockFile.unlock('some-file.lock', function (er) {
    // er means that an error happened, and is probably bad.
  })
})

Methods

Sync methods return the value/throw the error, others don't. Standard node fs stuff.

All known locks are removed when the process exits. Of course, it's possible for certain types of failures to cause this to fail, but a best effort is made to not be a litterbug.

lockFile.lock(path, [opts], cb)

Acquire a file lock on the specified path

lockFile.lockSync(path, [opts])

Acquire a file lock on the specified path

lockFile.unlock(path, cb)

Close and unlink the lockfile.

lockFile.unlockSync(path)

Close and unlink the lockfile.

lockFile.check(path, [opts], cb)

Check if the lockfile is locked and not stale.

Callback is called with cb(error, isLocked).

lockFile.checkSync(path, [opts])

Check if the lockfile is locked and not stale.

Returns boolean.

Options

opts.wait

A number of milliseconds to wait for locks to expire before giving up. Only used by lockFile.lock. Poll for opts.wait ms. If the lock is not cleared by the time the wait expires, then it returns with the original error.

opts.pollPeriod

When using opts.wait, this is the period in ms in which it polls to check if the lock has expired. Defaults to 100.

opts.stale

A number of milliseconds before locks are considered to have expired.

opts.retries

Used by lock and lockSync. Retry n number of times before giving up.

opts.retryWait

Used by lock. Wait n milliseconds before retrying.